Backside-Illuminated Imager Textured Region Infrared Absorption
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional silicon-based photodetecting imagers have limited absorption and detection properties for infrared light due to silicon's indirect bandgap semiconductor nature, making them inefficient for wavelengths longer than 1100 nm, and require substantial path lengths and absorption depths to detect photons effectively.
Innovation Solution
The development of backside-illuminated photosensitive imager devices with a textured region and passivation region that increases the absorption path length for longer wavelengths, allowing for enhanced absorption of infrared radiation within a thin semiconductor material, and includes a textured region with surface features to diffuse and redirect electromagnetic radiation, increasing quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon-based photodetecting imagers are used for infrared detection, then visible light detection is effective, but absorption of electromagnetic radiation with wavelengths greater than 1100 nm is very low
Solution Approach 1:
The patent transitions from front-side illumination to backside illumination architecture, changing the dimensional approach to light interaction. By illuminating the semiconductor substrate from the backside, light travels through the entire thickness of the substrate before reaching the photosensitive region, effectively increasing the absorption path length and enabling detection of longer wavelengths up to 1700 nm
Solution Approach 2:
The patent modifies the optical path length parameter by changing the illumination geometry and substrate thickness. Using a thin substrate (5-50 μm) with backside illumination creates an optimized path length that enhances absorption for near-infrared wavelengths while maintaining visible light detection capability
2Ease of operation
If electromagnetic radiation is incident on the semiconductor surface containing CMOS devices and circuits, then front side illumination works, but absorption path length is limited
Solution Approach 1:
The patent inverts the traditional front-side illumination approach by implementing backside illumination. The semiconductor substrate is illuminated from the opposite side, allowing light to traverse the entire substrate thickness before reaching the photosensitive region, thereby maximizing the absorption path length without complicating the CMOS device operation
3Reliability
If a textured region is added to increase absorption path length, then infrared absorption is enhanced, but device complexity increases
Solution Approach 1:
The patent introduces a textured region with curved or non-planar surface features on the backside of the substrate. This curvature increases the optical path length and light scattering, enhancing absorption efficiency for infrared wavelengths while maintaining a relatively simple single-layer structural addition
4Reliability
If substrate thickness is increased to increase absorption depth, then infrared detection improves, but manufacturing difficulty increases
Solution Approach 1:
The patent optimizes the substrate thickness parameter to a specific range (5-50 μm) that balances absorption efficiency with manufacturability. This thin substrate thickness provides sufficient absorption path length for near-infrared wavelengths while remaining compatible with standard semiconductor fabrication processes and reducing manufacturing complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These devices achieve improved response in the near-infrared spectrum and enhanced quantum efficiency, with quantum efficiency exceeding 60% in the visible region and increased responsivity for wavelengths greater than 1000 nm, enabling efficient conversion of electromagnetic radiation to electrical signals.
Implementation Method 1
a textured region with surface features to diffuse and redirect electromagnetic radiation, increasing quantum efficiency
Implementation Method 2
enhanced absorption of infrared radiation within a thin semiconductor material
Implementation Method 3
CMOS sensors are typically manufactured from silicon and can covert visible incident light into a photocurrent
Data Source
AI summary
Backside illuminated photosensitive devices and associated methods are provided. In one aspect, for example, a backside-illuminated photosensitive imager device can include a semiconductor substrate having multiple doped regions forming a least one junction, a textured region coupled to the semiconductor substrate and positioned to interact with electromagnetic radiation, and a passivation region positioned between the textured region and the at least one junction. The passivation region is positioned to isolate the at least one junction from the textured region, and the semiconductor substrate and the textured region are positioned such that incoming electromagnetic radiation passes through the semiconductor substrate before contacting the textured region. Additionally, the device includes an electrical transfer element coupled to the semiconductor substrate to transfer an electrical signal from the at least one junction.